Osteology

Question 1

Answer 1

Question 2

Answer 2

Question 3

What exits the skull through the superior orbital fissure?

Answer 3

CN 3, 4 and 6

Lacrimal, frontal and nasociliary branches of opthalmic nerve (V1 of CN 5)

Opthalmic veins and vessels

Question 4

Answer 4

Question 5

What exits the skull through the supraorbital foramen?

Answer 5

Supraorbital nerve, vein and artery (branch of V1 of trigeminal)

Question 6

What exits the skull through the infraorbital foramen?

Answer 6

Infraorbital nerve, artery and vein (branch of V2 of trigeminal)

Question 7

What exits the skull through the inferior orbital fissure?

Answer 7

Maxillary nerve (V2 of CN 5)

Question 8

Answer 8

Question 9

What is the pterion and what is its clinical significance?

Answer 9

Pterion is the point where the greater wing of the sphenoid bone, the frontal bone, the parietal bone and the temporal bone all join together. It is a site of weakness in the skull so it is prone to injury in head trauma. Its internal surface is also traversed by the middle meningeal artery, so the pterion is the most common site of damage to the MMA.

Question 10

What exits the skull through the foramen magnum?

What enters the skull through the foramen magnum?

Answer 10

Exits:

• Medulla
• Spinal cord
• Vertebral arteries

Enters:

• Spinal roots of CN 11

Question 11

What exits the skull through the jugular foramen?

Answer 11

CN 9

CN 10

CN 11

Question 12

What exits the skull through the optic canal?

Answer 12

Optic nerve

Opthalmic artery

Question 13

What exits the skull through the foramen rotundum?

Answer 13

Maxillary nerve (V2 of CN 5)

Question 14

What exits the skull through foramen ovale?

Answer 14

Mandibular nerve (V3 of CN 5)

Lesser petrosal nerve (branch of CN 9)

Question 15

What exits the skull through foramen spinosum?

Answer 15

Middle meningeal artery and vein

Meningeal branch of mandibular nerve (V3 of CN 5)

Question 16

What exits the skull through foramen lacerum?

Answer 16

Greater petrosal nerve

Question 17

What exits/enters the skull through the carotid canal?

Answer 17

Internal carotid artery

Internal carotid nerve plexus

Question 18

What exits the skull through the internal acoustic meatus?

Answer 18

CN 7 and CN 8

Question 19

What exits the skull through the hypoglossal canal?

Answer 19

CN 12

Question 20

What is the function of the skull in general? (3)

Answer 20

• Bony foundation for special sense organs (sight, sound, smell, taste)
• Houses and protects the brain
• Connects to the vertebral column

Question 21

• What is the piriform aperture?
• What are the inferior, middle, and superior nasal concha?
• What is their purpose?

Answer 21

• Pear-shaped; anterior nasal opening in the cranium
• Curved bony plates in the nasal septum
• Increase surface area so that air can be warmed and humidified before reaching the lungs

Question 22

What exits the skull through the mental foramen?

Answer 22

Mental nerve (branch of mandibular nerve, V3 of CN 5)

Question 23

Which bones form the orbit?

Answer 23

Frontal

Zygomatic

Sphenoid

Lacrimal

Ethmoid

Palatine

Question 24

The size of the orbit is large relative to the size of an eyeball. Why is there such a size discrepancy?

Answer 24

• Shape helps to stabilize eye in socket
• Needs to allow space for 6 EOMs, optic nerve, lacrimal apparatus, fascia, adipose tissue, and the neurovascular structures which supply these tissues

Question 25

What type of joint joins the bones of the calvaria?

Answer 25

* Serrated immovable sutures * separated by a thin layer of fibrous connective tissue that is continuous with the periosteum * become less distinct with age

Question 26

Name one structure that attaches to the external occipital protuberance?

Answer 26

Ligamentum Nuchae

Question 27

How is the mandible attached to the skull?

Answer 27

TMJ – synovial joint head of the mandible with mandibular fossa of temporal bone

Question 28

What is the lambda and the bregma?

Answer 28

Point where the saggital suture meets the lambdoid and coronal sutures, respectively

Question 29

What is the asterion?

Answer 29

Junction of parietomastoid, occipitomastoid and lambdoid sutures

Question 30

Answer 30

Question 31

What parts of the brain are situated in each cranial fossa? (anterior, middle, posterior)

Answer 31

Anterior - inferior and anterior parts of the frontal lobes of the brain Middle – temporal lobes and pituitary Posterior - cerebellum, pons, and medulla oblongata

Question 32

Describe the separation between the anterior and middle cranial fossae.

Answer 32

* The middle cranial fossa is behind and below the anterior cranial fossa * Separated by the lesser wings of the sphenoid bones laterally and two sharp bony projections, the anterior clinoid processes, medially

Question 33

What is the purpose of the frontal sinus?

Answer 33

The frontal sinus is an air cavity in the frontal bone that is presumably to decrease the bone's weight. The total volume of the air spaces in bones with these air cavities increases with age.

Question 34

* What is the sella turcica? * What structure is situated in the sella turcica?

Answer 34

* The sella turcica (Turkish saddle) is the saddle-like bony formation on the upper surface of the body of the sphenoid, which is surrounded by the anterior and posterior clinoid processes. * The pituitary gland - clinoid means “bedpost,” and the four processes (two anterior and two posterior) surround the hypophysial fossa, making the “bed” of the pituitary gland, like the posts of a four-poster bed.

Question 35

For the atlanto-occipital joint: * Type of joint? * Points of articulation? * Movements permitted?

Answer 35

* Synovial joint with no articulating disc * Articulations are between the superior articular surfaces of the lateral masses of the atlas and the occipital condyles * Primarily flexion (nodding of the head) but also permit a little lateral flexion and rotation

Question 36

Where is the tectorial membrane located?

Answer 36

The tectorial membrane is the strong superior continuation of the posterior longitudinal ligament that broadens and passes posteriorly over the median atlanto-axial joint and its ligaments. It runs superiorly from the body of C2 through the foramen magnum to attach to the central part of the floor of the cranial cavity, formed by the internal surface of the occipital bone.

Question 37

Answer 37

Question 38

Answer 38

Question 39

Answer 39

Question 40

Answer 40

Question 41

Answer 41